Fixed price only works if you defend the scope
Everyone likes a fixed price until the third small addition. The number holds because of a written rule, not goodwill.
Fixed price is the thing clients ask for most and the thing agencies are worst at honouring. The failure is almost never dishonesty — it is that nobody wrote down what happens when the scope moves, so it moves for free until the margin is gone and the relationship is worse for it.
We handle it with one rule, agreed before anything is built: a change is priced in writing, and it is ticketed as new work rather than absorbed into the current sprint. Not a negotiation, not an argument at the end. Two lines in the statement of work, applied every single time.
The counter-intuitive part is that clients like this more, not less. A change request that comes back within a day with a number attached is a decision they get to make. Silent absorption is a decision made for them, and they find out about it in the last week when the date slips.
It also protects the thing they actually bought. A fixed date is only real if the work behind it is fixed too. Every hour spent on an unpriced addition is an hour not spent on what was agreed, and the client discovers that trade at the worst possible moment.
The discipline has a cost on our side. It means saying no in writing, quickly, to someone you like working with — which is uncomfortable often enough that it has to be a rule rather than a preference.
Written by the Valentir team. If you want to argue with any of it, that is what hello@valentir.in is for.